Conventionally, printing apparatuses using an inkjet printhead (to be referred to as a printhead hereinafter) are widely used in, e.g., printers and copying machines because of advantageous features such as quietness, low cost, low running cost, and small size.
A serial printing apparatus as one form of inkjet printing apparatuses executes printing by discharging ink to a printing medium while serially scanning a printhead (the scanning direction is called a main scanning direction). An operation of conveying the printing medium in a direction perpendicular to the scanning direction of the printhead is repeated in every scanning, thereby completing printing of one page of the printing medium.
Of these printing apparatuses, especially, a low-end printing apparatus reduces the cost by decreasing the print buffer capacity. More specifically, the print buffer capacity is smaller than the amount of print data to be used for printing in one printhead scanning. Particularly in color printing, an amount of color print data to be used for printing on a printing medium in one scan cycle is divided into a plurality of print blocks. Data of each print block is transferred from the host to the printing apparatus, thereby executing print control.
Examples of the apparatus are disclosed in Japanese Patent Publications Laid-Open Nos. 9-123527 and 10-175333.
However, to achieve high-quality printing required of recent printing apparatuses, the print data amount transferred from the host must be large. The above-described conventional arrangement takes too much time for print data transfer. The data transfer is too slow to execute high-speed printing.
Especially, in so-called multi-pass printing that is executed by scanning the printhead a plurality of number of times in the same region of a printing medium, the following problem arises with regard to each pass printing. Data necessary for printing of an entire region to be printed by multi-pass printing is transferred from the host, although not all the necessary data is used for actual printing. When the data amount increases, the transfer load becomes heavy. Hence, it is impossible to cope with high-speed multi-pass printing.